A correct detection and appropriate identification of causal pathogens associated with crop plants or seeds are considered to be the most important issue in designing the proper management plans for plant diseases. This study was designed to detect Phytophthora infestans inoculum from potato grown soil. A high detection rate of P.infestans was obtained from the naturally infested soil of potato fields. Naturally soils were firstly moistened in a plastic pots and then pre-incubated at ±18°C for 3 days, baiting with potato tuber slice for 24, 48, and 72 h. The baits were then thoroughly washed, flooded with 10–15 ml of distilled water in Petri-dishes and incubated under continuous darkness in chamber ±18ºC. Sporangia started to emerge from the margins of potato tuber slice. They were easily observed under the stereomicroscope. Pure culture of the fungus was obtained by isolating from baited tubers on a Rye Agar medium. This is the first report of recovery of P. infestans from naturally infested potato growing soils using susceptible potato tuber (K. Bahar) as bait in India. All isolates were determined to be A2 mating type.

This study was conducted in 2017 under greenhouse conditions using selected four different potato clones to determine the effects of different doses of GA3 and arbuscular mycorrhizal fungus on mini tuber production. The research, carried out in a randomized complete block design with three replications, applied GA3 doses of 0, 5, 10, and 15 ppm, and mycorrhizal inoculat doses of 0, 500, 1250, and 2000 mg/100 tubers. Parameters including emergence time, plant height, main stem number, tuber number, average tuber weight, tuber size distribution (>45 mm, 28-45 mm, <28 mm), and maturity period were examined. The effect of GA3 application on all investigated parameters except the number of main stems was significant, statistically. The highest mini tuber number (9.1 tubers) and mini tuber yield (408.4 g/pot) were obtained from the application of 15 ppm GA3, while the highest average mini tuber weight (46.74 g) was obtained from the control group. In mycorrhizal applications, the highest tuber number was obtained at a dose of 500 mg/100 tubers, and the highest mini tuber weight and yield were obtained at a dose of 1250 mg/100 tubers. As a result of the study, it was determined that the application of 15 ppm GA3 is suitable due to its positive effect on mini tuber multiplication, and the mycorrhizal application at a dose of 500 mg/100 tubers is appropriate due to its positive effect on increase of tuber number.